package envoy.client.util;

import java.util.*;
import java.util.stream.*;

import javafx.scene.Node;

/**
 * @author Leon Hofmeister
 * @since Envoy Client v0.2-beta
 */
public final class ReflectionUtil {

	private ReflectionUtil() {}

	/**
	 * Gets all declared variable values of the given instance that have the specified class.
	 * <p>
	 * (i.e. can get all {@code JComponents} (Swing) or {@code Nodes} (JavaFX) in a GUI class).
	 * <p>
	 * <b>Important: If you are using a module, you first need to declare <br>
	 * "opens {your_package} to envoy.client.util;" in your module-info.java</b>.
	 *
	 * @param <T>          the type of the object
	 * @param <R>          the type to return
	 * @param instance     the instance of a given class whose values are to be evaluated
	 * @param typeToReturn the type of variable to return
	 * @return all variables in the given instance that have the requested type
	 * @throws RuntimeException if an exception occurs
	 * @since Envoy Client v0.2-beta
	 */
	public static <T, R> Stream<R> getAllDeclaredVariablesOfTypeAsStream(T instance,
		Class<R> typeToReturn) {
		return Arrays.stream(instance.getClass().getDeclaredFields())
			.filter(field -> typeToReturn.isAssignableFrom(field.getType())).map(field -> {
				try {
					field.setAccessible(true);
					return typeToReturn.cast(field.get(instance));
				} catch (IllegalArgumentException | IllegalAccessException e) {
					throw new RuntimeException(e);
				}
			});
	}

	/**
	 * Gets all declared variables of the given instance that are children of {@code Node}.
	 * <p>
	 * <b>Important: If you are using a module, you first need to declare <br>
	 * "opens {your_package} to envoy.client.util;" in your module-info.java</b>.
	 *
	 * @param <T>      the type of the instance
	 * @param instance the instance of a given class whose values are to be evaluated
	 * @return all variables of the given object that have the requested type as {@code Stream}
	 * @since Envoy Client v0.2-beta
	 */
	public static <T> Stream<Node> getAllDeclaredNodeVariablesAsStream(T instance) {
		return getAllDeclaredVariablesOfTypeAsStream(instance, Node.class);
	}

	/**
	 * Gets all declared variables of the given instance that are children of {@code Node}<br>
	 * <p>
	 * <b>Important: If you are using a module, you first need to declare <br>
	 * "opens {your_package} to envoy.client.util;" in your module-info.java</b>.
	 *
	 * @param <T>      the type of the instance
	 * @param instance the instance of a given class whose values are to be evaluated
	 * @return all variables of the given object that have the requested type
	 * @since Envoy Client v0.2-beta
	 */
	public static <T> List<Node> getAllDeclaredNodeVariables(T instance) {
		return getAllDeclaredNodeVariablesAsStream(instance).collect(Collectors.toList());
	}
}